1. Field of Invention
The invention relates to a reciprocating piston internal combustion engine with a variable compression ratio.
2. Description of the Prior Art
In reciprocating piston internal combustion engines with charge control and unvariable compression ratio the compression end pressure and thereby the thermodynamic degree of efficiency is considerably reduced during the partial load operation in view of the reduced charge, so that the specific fuel consumption increases during the partial load operation. In order to prevent this disadvantage it is known to vary the compression ratio by changing the volume of working chamber in such a manner that substantially the same compression and pressure is achieved throughout the total operating range of the internal combustion engine.
In a known reciprocating piston internal combustion engine (DE-PS No. 705 283) in accordance with the preamble of claim 1, a rod is provided for turning the second piston part, which forms the piston head, with respect to the first piston part which is connected with the piston rod, whereby the rod extends through the second piston part and is mounted in the piston axis, while being in engagement with an inner gear on the said piston part by means of gear wheels, further extending through the bushing and non-rotatably connected with an encompassing tube which is provided with an outer gear being in camming engagement with the inner gear of the bushing. The second piston part is turned with respect to the first piston part by turning this rod, thus changing the position of the second piston part with respect to the cylinder head by means of the thread being mounted between these parts, whereby the volume of the working chamber and thereby also the compression ratio is changed. However, this known device is rather expensive, since a double piston rod has to be used in view of the centric disposition of the rod, and in view of the fact that the rod also has to move with the piston movement, so that a complicated mechanism is required for turning the rod.